Self-tapping replacement stud with chip collection and storage chamber

ABSTRACT

A self-tapping replacement stud, for use in assembled engine blocks and similar workpieces in which the original threads of a stud bore have been inadvertently stripped, including an elongated shank having opposite ends and providing screw threads circumscribing one end, a collecting bore extended through the threads transversely of the shank bounded by a cutting edge adapted to form female threads in the stud bore when rotated therein, a stud driver adapted to be releasably attached to the end of the shank opposite to the threaded end engageable with the workpiece for controlling the depth of penetration of the threaded end into the stud bore, the collecting bore constituting a chamber for receiving and retaining the cuttings from the forming of new threads within the stud bore to avoid their being dropped into the workpiece, such as the crankcase of an engine.

United States Patent 1191 Brooks [4 1 July 23, 1974 SELF-TAPPINGREPLACEMENT STUD WITH CHIPCOLLECTION AND STORAGE CHAMBER [76] Inventor:Daryl G. Brooks, 5240 N. Van Ness,

Fresno, Calif. 93705 [22] Filed: July 17, 1972 [21] App]. No.: 272,376

Related US. Application Data [63] Continuation-impart of Ser. No.156,319, June 24,

1971, abandoned.

3/1958 Australia 85/47 9/1920 Great Britain 81/5312 5/1903 Great Britain85/47 Primary Examiner-Edward C. Allen Attorney, Agent, or Firm-Huebner& Worrel [5 7 ABSTRACT .A self-tapping replacement stud, for use inassembled engine blocks and similar workpieces in which the originalthreads of a stud bore have been inadvertently stripped, including anelongated shank having oppo- Csite ends and providing screw threadscircumscribing one end, a collecting bore extended through the threadstransversely of the shank bounded by a cutting edge adapted to formfemale threads in the stud bore when rotated therein, a stud driveradapted to be releasably attached to the end of the shank opposite tothe threaded end engageable with the workpiece for controlling the depthof penetration of the threaded end into the stud bore, the collectingbore constituting a chamber for receiving and retaining the cuttingsfrom the forming of new threads within the stud bore to avoid theirbeing dropped into the workpiece, such as the crankcase of an engine.

6 Claims, 8 Drawing Figures SELF-TAPPING REPLACEMENT STUD WITH CHIPCOLLECTION AND STORAGE CHAMBER CROSS REFERENCE TO RELATED APPLICATIONThis application is a continuation-in-part of my copending applicationSer. No. l56,3l9, filed June 24, 1971 and now abandoned, entitledSelf-Tapping Re placement Stud With Chip Collection And Storage Chamber.

BACKGROUND OF THE INVENTION The present invention relates to aself-tapping replacement stud for stripped stud bores and moreparticularly to such a replacement stud which has selftapping threadsand which automatically receives and confines cuttings produced by thetapping action to preclude their dispersal into any associatedmechanism.

It is a well known problem in the reassembly of overhauled engines ofvarious types having a plurality of threaded stud receiving bores thatsuch bores can be inadvertently stripped of their threads during thetorquing operation. Normally the strippedbor e is drilled out and anover-size female threaded plug is installed to renew the threads, or theexisting bore is tapped out to a larger size to receive an over-sizebolt or stud. Both are tedious, time consuming and thus expensiveoperations.

A particular problem exists in some types of engines in which the borescommunicate with the interior of the engine block or crankcase. This istrue of certain types of automobile engines where elongated studs holdthe cylinder blocks and heads in assembly with the crankcase. Inreassembly after a major overhaul of such an engine, stud nuts must betightened using a torque wrench to hold the head, block and crankcase incompressive assembled relation. During this torquing operation, thestuds are often accidentally excessively rotated and the threadsstripped from within their threaded stud bores in the crankcase. Whenthe stud bores are drilled out or retapped in the conventional manner,the cuttings from the operation drop inwardly into the interior of thecrankcase. Asa result, the engine must be disassembled and thoroughlycleaned to remove such cuttings which'is time-consuming, tedious andexpensive. The replacement stud of the present invention eliminates anynecessity for such additional cleaning and reassembly procedures.Further, it can'be dependably anchored in a stripped bore virtuallyasquickly and easily as the original stud can be mounted in an undamagedbore and without subjecting any associated mechanism to chips, cuttingsor other debris normally incident to tapping operations.

SUMMARY OF THE INVENTION Therefore, it is an object of the presentinvention to provide an improved replacement stud having selftappingthreads for use in rebuilding engines.

Another object is to provide such a replacement stud which has acollection chamber automatically to collect and retain the cuttingsproduced by the self-' tapping threads as the replacement stud isinstalled within a stud bore.

Another object is to provide such a replacement stud in which thecuttings are automatically sealed within the collection chamber.

Another object is to provide such a replacement stud which precludes thedropping of cuttings into the interior of an engine block during thescrewing home of the replacement stud within the stud bore.

Another object is to provide such a replacement stud which obviates thenecessity of disassembling an engine in order to clean the cuttings fromthe interior of the engine after retapping threads within a strippedstud bore.

Another object is to provide such a replacement stud which has areleasable stud driver at one endv thereof which is adjustableselectively to define the maximum depth of penetration of thereplacement stud within a stud bore and is thereafter removable topermit the attachment and tightening down of a stud nut on thereplacement stud.

Another object is to provide such a replacement stud which eliminatesthe necessity for employing several tools in order to install areplacement stud.

Another object is to provide such a replacement stud which minimizes theexpenditure of time involved in reassembling an overhauled engine.

Another object is to provide such a replacement stud which may take avariety of shapes and sizes for use in many different types of engines.

Another object is to provide such a replacement stud which is easy tooperate.

Further objects and advantages are to provide improved elements andarrangements thereof in a device for the purposes described which isdependable, economical, durable, and fully effective in accomplishingits intended purposes.

I cylinders andhead of one type of engine in a partially assembledcondition showing the installation of the self-tapping replacement studof the present invention.

FIG. 2 is a fragmentary, transverse, vertical section of the partiallyassembled engine of FIG. 1 showing the replacement stud of the presentinvention screwed home to its maximum depth of permitted penetrationwithin the stud bore as defined by the stud driver attached to thereplacement stud.

FIG. 3 is a somewhat enlarged fragmentary view of the tapered end of thereplacement stud partially threaded into astripped stud bore in thehousing shown fragmentarily in vertical section'and showing therelationship' of the collection chamber to the cutting zone of theself-tapping threads.

FIG. 4 is a somewhat enlarged fragmentary view of the upper portionofthe replacement stud of the present invention showing the stud driver invertical section thereon.

FIG. 5'is a perspective viewof the stud driver of the present invention.

FIG. 6 is a side elevation of a second form of replace- I taken on FIG.8 is a fragmentary development view of the periphery of the tapping endportion of the second form of stud of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The shank 11 is of a maximumdiameter which is a predetermined size larger than that of a stud borein which it is designed to be used. Similarly, the length of the shankis governed by the design of the engine or other workpiece in which itis intended to be mounted.

For illustrative purposes, the proportions of the replacement stud hereshown are for use in a well-known make of automobile engine, but it isrecognized that the shape and size of the embodiments of the replacementstud can be varied a great degree within the scope of the invention toaccommodate a like variety of engines and other work objects.

A set of male screw threads 14 is formed about the upper portion 12 ofthe shank 11 and extends down the shank a sufficient dstance fordependable engagement therewith. The lower portion 13 of the shankprovides a tapered end 15 which downwardly constricts from the diameterof the shank to a diameter somewhat smaller than that of the stud borein which it is designed to be used. A set of self-tapping threads 16 isintegrally formed about the tapered end and extends up the shank untilreaching its full diameter. A cutting zone 20 is defined by theself-tapping threads and extends from approximately the point where theshank begins to taper to the point where the diameter of the tapered endbecomes smaller than that of the stud bore in which it is designed to beused.

A chip collection chamber 21 is provided in the tapered end of the shankwithin the cutting zone and consists essentially of a bore runningdiametrically through the shank, as best shown in FIG. 3. At oppositeends, the bore is bounded by cutting edges 22 which actually performtheintended tapping operations.

An hexagonal stud driver 23 having an upper end 24 and a lower end 25isthreadably received on the upper portion 12 of the shank 11. The studdriver has a passage 26 running axially therethrough. Half of thepassage adjacent to the lower end of the stud driver has internal screwthreads 31 into which the screw threads 14 of the shank are threadablyreceived. The remaining half of the passage adjacent to the upper end ofthe stud driver is of a slightly larger diameter than that of thethreaded half of the passage and has a smooth surface. The lower end ofthe stud driver provides an axially disposed annular bearing surface 32.A lock bolt 33 is received in the passage at the upper end of the studdriver. The lock bolt has a threaded end 34 and a .wrench head 35. Thethreaded end is threadably received in the internal screw threads 31 ofthe passage, as best shown in FIG. 4.

The replacement stud 10 of the present invention is shown forillustrative purposes for use in a particular type of automobile enginegenerally indicated at 40. As shown in FIGS. 1 and 2, such an automobileengine is in the process of reassembly and as thus far reassembled, theengine includes a crankshaft housing or crankcase 41, cylinder block 42,and a head 43. An original stud is shown at 44. The crankshaft housinghas an interior 45 and the headhas an upper surface 46. Severalunthreaded stud bores 50 extend vertically through the head 43. Severalcorresponding, aligned, internally threaded stud bores 51 are providedin the crankshaft housing. When the crankshaft housing, block and headare assembled, as shown in FIGS. 1 and 2, the stud bores 50 and 51 arepaired in corresponding vertical alignment. A stripped stud bore isrepresented at 52 in FIGS. 1 and 3.

SECOND FORM scribed in connection with-the first form. The cuttingportion is endwardly taperedand circumscribed by tapping threads 66. Ina commercial version of the subject invention, the end tapers from 0.320inches in diameter at the extreme end to full diameter, 27/64 inches atthe third full thread, or in 0.200 inches. A bore 67 is extendedtransversely through the threads 66 of the cutting portion andconstitutes a collection chamber. At opposite sides of the shank, thebore is bounded by cutting edges 68. While the bore22 of the first formis extended diametrically through the shank 11 in right angular relationto the axis thereof, the bore 67 is extended substantially diametricallythrough the shank 61 in a plane common to the axis of the shank but itis obliquely related to the axis in said plane. In the exemplarycommercial version, the bore is 3/16 inches in diameter and is formed ata angle with respect to the axis of the stud. This is 15 relative to theradius. The bore is positioned so that the lower edge of its loweropening is adjacent to the upper end of the taper, shown by the dashedline 69, and so that its upper opening is above the upper end of thetaper, as best shown in FIGS. 7 and 8. Thus, the cutting edges 68 areslightly displaced from each other axially of the shank 61 and aretherefore disposed in threads 66 of slightly different diameters due tothe tapered formation of the end of the stud. This has been found to behighly desirable for several reasons. The cutting edges exercise a dualcutting action. That is, threads started by the cutting edge of the endof the bore nearer the end of the stud are traced by the cutting edge ofthe end of the bore farther from the'end of the stud. The cutting edgesaxially spaced in the stud accommodate stripped stud bores 52 which varysomewhat in diameter. By angling the bore it has a somewhat greaterstoring capacity. In all instances, however, both ends of the bore 67are overlaid by the crankcase 41 whenever the cutting end isinsertedinto a stripped bore 52 to a depth sufficient for either of thecutting edges to commence their tapping action. Thus all chips resultingfrom the tapping action are captured and permanently confined in thebore.

OPERATION The operation of the described embodiments of the subjectinvention is believed to be clearly apparent and is briefly summarizedat this point. When a stud bore 52 becomes stripped and it is desired toreassemble the engine 40, the self-tapping replacement stud or 60 of thepresent invention can be employed to avoid the previously requiredlaborious task of removing the crankcase 41, boring out the strippedstud bores 52, tapping new threads in the enlarged stud bores, cleaningthe cuttings from the interior 45 of the crankshaft housing, and finallyreassembling the engine.

When the stud bore 52 is stripped, the original stud 44 in the strippedstud bore is first removed. In order to prepare the self-tappingreplacement stud 10 or 60 for use in the stripped stud bore 52, the studdriver 23 is locked in a preselected position on the upper portion 12 or62 of the shank 11 or 61. The length of the screw threads 14 and 64along the upper portions of the shanks is sufficiently great that thestud driver 23 can be positioned throughout a relatively long range ofdistances from the tapered ends 15 and 63 of the shanks. Properpositioning of the stud driver is accomplished by first measuring thevertical distance from the interior side 45 of the crankcase 41 to theupper surface 46 of the cylinder cover 43 when the housings and coverare assembled as shown in FIG. 2. The stud driver is then threadablypositioned on the shank so that the bearing surface 32 is this samedistance from the tenninus of the tapered end of the shank. The lockbolt 33 is then threaded into the screw threads 31 in the passage 26 ofthe stud driver until the remote portion of the threaded end 34 of thelock bolt is in facing engagement with the upper portion 12 or 62 of theshank, as shown in FIG. 4. The bolt thus serves as a jamb bolt and thestud driver is thus locked in position on the shank on which it ismounted.

The replacement studs 10 and 60 are installed by first passing theirshanks 11 and 61 through the stud bore 50 and downwardly until thetapered ends l5and 63 of the shanks are in nesting engagement with thestripped stud bores 52. Since the shanks are of a somewhat largerdiameter than the stripped stud bores, the tapered ends extend into thestripped stud bores only the lengths of the portions thereof having adiameter smaller than that of the bore. The point of contact of thetapered end is within the cutting zone of the first form and within therange of the opposite ends of the bore in the second form. The cuttingedges 22 and 68 are located in the cutting zones and come intoengagement with the walls of the stud bore as the collecting bores 21and 67 enter the stud bores and thus are overlaid and closed by thecrankcase 41. Using any conventional wrench engaged with the head 35' ofthe stud driver 23, the shank is rotated in a normal clockwise directionwhile pressure is exerted downwardly on the replacement stud whilemaking certain that a vertical attitude is maintained. The self-tappingthreads 16 or 66 are thereby driven into the stripped stud bore 52tapping out new threads and simultaneously screwing the replacement studhome in the renewed threads. Cuttings or chips are produced by thetapping out of the new threads by the cutting edges. As the cuttings orchips are formed they are received by the collection chambers or bores21 and 67. Since both ends of the bores are overlaid ,and sealed by thewalls of the stud bore, none of the cuttings or chips can escape fromsuch bores into the crankcase 41. Since the replacement studs arepermanently installed, once they are screwed home, or at least installeduntil their removal from the crankcase may become desirable during somesubsequent engine disassembly, the cuttings and chips are in effectpermanently encapsulated within the bores or at least captured thereinuntil some eventual disassembly of the engine makes removal of thereplacement studs desirable.

When the bearing surface 32 of the stud driver 23 contacts the uppersurface 46 of the cylinder cover 43, the replacement stud has beeninstalled at its intended depth of penetration within the stud bore 52.It will again be noted that, as shown in FIG. 2, the collection chamberor bore 21 is completely enclosed within the stud bore. The same is trueof the collectingbore 67 of the second form when it is installed. Thecuttings are thereby sealed withinthe collection chamber and areprevented from being jostled out to fall into the interior of thecrankcase 41. So installed, the replacement studs are dependably andsecurelyanchored in place.

The jamb bolt 33 is then unscrewed from the stud driver 23and'the studdriver unscrewed from the upper ends 24 or 62 of the installedreplacement stud. A stud nut, not shown, can then be threadably receivedon the screw threads 14 or 64 of the upper portion of the shank andtightened to the desired extent so as securely to hold the crankcase 41,cylinder block 42, and head 43 in the assembled relation shown in FIGS.1 and 2.

It will be seen that one stud driver 23 and lock bolt 33 are all thatneed be maintained on hand to be used. with the replacement studs. Itwill also be seen that necessity for maintaining thread tapping tools onhand for this purpose is avoided. The replacement studs can be installedwithout getting cuttings or chips in the crankcase. Thus a stripped studcan be replaced without disassembling and cleaning the engine. Thereplacement studs of the present invention have saved so much time andlabor in performing many engine repair services thatthecosts thereofhave been reduced to a fraction of those previously required.

Although the invention has been herein shown and described in what areconceived to be the most practical and preferred embodiments, it isrecognized that departures may be made therefrom within the scope of theinvention, which is not to be limited to the-illustrative detailsdisclosed.

I claim:

1. A stud for anchored engagement in a bore of a workpiece comprising anelongated rod adapted for rotation about a longitudinal axis having. ascrewthreaded cutting end and a distal end, the cutting end beingcircumscribed by screw threads and being endwardly tapered from aposition intermediate opposite ends of the screw threads whereby saidscrew threads.

have a portion of substantially uniform diameter and an endwardlytapered portion, and a collecting bore extended obliquely through therod having opposite ends providing thread cutting edges adapted to cutfemale threads in the workpiece when the rod is rotated in the borethereof and to discharge chips resulting from thread formation into thecollecting bore, one of said ends of the bore being in the taperedportion of the threads but overlapping said position and the other endof the bore opening into the screw threads of uniform diameter so as tobe tightly overlaid by the workpiece when the cutting edges are in thebore of the workpiece to capture such chips in the collecting bore asthey-are formed and when the rod is anchored in the bore permanently toretain the chips in the collecting bore.

2. The stud of claim 1 including means on the rod having a bearingsurface disposed toward the workpiece and engageable therewith to limitdepth of engagement of the cuttingend in the workpiece whereby the screwthreads of uniform diameter can be tightened in the bore of theworkpiece with opposite ends of the collecting bore being overlaidthereby.

3. A self-tapping replacement stud having a screwthreaded tapping endfor anchored engagement in a bore in a first workpiece, a shank forrotatable extension through a bore in a second associated workpiece anda screw-threaded opposite end, the tapping end being circumscribed byscrew threads and being endwardly tapered from a position intermediateopposite ends of the screw threads whereby said screw threads have aportion of substantially uniform diameter slightly greater than that ofthe bore of the first workpiece and an endwardly tapered portion; acollecting bore extended obliquely therethrough having an end opening inthe tapered portion of the threads but overlapping said position and anopposite end in the portion of the threads of uniform diameter, each ofthe ends of the bore being bounded by a cutting edge and oppositeextremities of the cutting edges being in portions of said end ofdifferent diameters with the opposite ends of the bore tightly overlaidby the first workpiece to encapsulate cuttings from the cutting edgestherein; a nut having a wrench head screw-threadably mounted on saidopposite end of the rod for adjustable positioning therealong providinga bearing face disposed toward the second workpiece engageable with thesecond workpiece to limit the depth of engagement of the tapping endwith the first workpiece; and a jamb bolt screw-threadably mounted inthe nut releasably engageable with the rod to secure the nut in adjustedposition thereon.

4. The combination of claim 3 in which the nut and jamb bolt areremovable to receive a nut on said opposite end of the rod for tightenedengagement with the 8 second workpiece to hold the workpieces incompressive engagement.

5. A self-tapping replacement stud comprising a rod having an endadapted for insertion into a stud bore of a workpiece, said end beingcircumscribed by screw threads and beingendwardly taperedfrorn aposition intermediate opposite ends of the screw threads whereby saidscrew threads have a portion of substantially uniform diameter slightlygreater than that of the stud bore and an endwardly tapered portion, anda bore extended obliquely through the rod having an end opening in thetapered portion of the threads but overlapping said position and anopposite end in the portion of the threads of uniform diameter, each ofthe ends of the bore being bounded by a cutting edge and oppositeextremities'of the cutting edges being in portions of said end ofdifferent diameters with the opposite ends of the bore tightly overlaidby the workpiece to incapsulate cuttings from the cutting edges therein.

6. A self-tapping replacement stud comprising a rod having an endadapted for insertion into a stud bore of a workpiece, said end beingcircumscribed by screw threads and being endwardly tapered from aposition intermediate opposite ends of the screw threads whereby saidscrew threads have a portion of substantially uniform diameter slightlygreater than that of the stud bore and an endwardly tapered portion, anda collecting bore extended obliquely through the rod in spaced relationto the end of the rod in a plane disposed diametrically and axially ofthe rod and having an end bounded by a cutting edge in the taperedportion of the threads but overlapping said position and having anopposite end bounded by a cutting edge disposed in the threads ofuniform diameter and each end of the opening being positioned so as tobe closed by the workpiece to capture the chips in the collecting borewhen said end of the rod is inserted into the stud openingsufficientlyto bring the cutting edges into workpiece engagement.

1. A stud for anchored engagement in a bore of a workpiece comprising anelongated rod adapted for rotation about a longitudinal axis having ascrew-threaded cutting end and a distal end, the cutting end beingcircumscribed by screw threads and being endwardly tapered from aposition intermediate opposite ends of the screw threads whereby saidscrew threads have a portion of substantially uniform diameter and anendwardly tapered portion, and a collecting bore extended obliquelythrough the rod having opposite ends providing thread cutting edgesadapted to cut female threads in the workpiece when the rod is rotatedin the bore thereof and to discharge chips resulting from threadformation into the collecting bore, one of said ends of the bore beingin the tapered portion of the threads but overlapping said position andthe other end of the bore opening into the screw threads of uniformdiameter so as to be tightly overlaid by the workpiece when the cuttingedges are in the bore of the workpiece to capture such chips in thecollecting bore as they are formed and when the rod is anchored in thebore permanently to retain the chips in the collecting bore.
 2. The studof claim 1 including means on the rod having a bearing surface disposedtoward the workpiece and engageable therewith to limit depth ofengagement of the cutting end in the workpiece whereby the screw threadsof uniform diameter can be tightened in the bore of the workpiece withopposite ends of the collecting bore being overlaid thereby.
 3. Aself-tapping replacement stud having a screw-threaded tapping end foranchored engagement in a bore in a first workpiece, a shank forrotatable extension through a bore in a second associated workpiece anda screw-threaded opposite end, the tapping end being circumscribed byscrew threads and being endwardly tapered from a position intermediateopposite ends of the screw threads whereby said screw threads have aportion of substantially uniform diameter slightly greater than that ofthe bore of the first workpiece and an endwardly tapered portion; acollecting bore extended obliquely therethrough having an end opening inthe tapered portion of the threads but overlapping said position and anopposite end in the portion of the threads of uniform diameter, each ofthe ends of the bore being bounded by a cutting edge and oppositeextremities of the cutting edges being in portions of said end ofdifferent diameters with the opposite ends of the bore tightly overlaidby the first workpiece to encapsulate cuttings from the cutting edgestherein; a nut having a wrench head screw-threadably mounted on saidopposite end of the rod for adjustable positioning therealong providinga bearing face disposed toward the second workpiece engageable with thesecond workpiece to limit the depth of engagement of the tapping endwith the first workpiece; and a jamb bolt screw-threadably mounted inthe nut releasably engageable with the rod to secure the nut in adjustedposition thereon.
 4. The combination of claim 3 in which the nut andjamb bolt are removable to receive a nut on said opposite end of the rodfor tightened engagement with the second workpiece to hold theworkpieces in compressive engagement.
 5. A self-tapping replacement studcomprising a rod having an end adapted for insertion into a stud bore ofa workpiece, said end being circumscribed by screw threads and beingendwardly tapered from a position intermediate opposite ends of thescrew threads whereby said screw threads have a portion of substantiallyuniform diameter slightly greater than that of the stud bore and anendwardly tapered portion, and a bore extended obliquely through the rodhaving an end opening in the tapered portion of the threads butoverlapping said position and an opposite end in the portion of thethreads of uniform diameter, each of the ends of the bore being boundedby a cutting Edge and opposite extremities of the cutting edges being inportions of said end of different diameters with the opposite ends ofthe bore tightly overlaid by the workpiece to incapsulate cuttings fromthe cutting edges therein.
 6. A self-tapping replacement stud comprisinga rod having an end adapted for insertion into a stud bore of aworkpiece, said end being circumscribed by screw threads and beingendwardly tapered from a position intermediate opposite ends of thescrew threads whereby said screw threads have a portion of substantiallyuniform diameter slightly greater than that of the stud bore and anendwardly tapered portion, and a collecting bore extended obliquelythrough the rod in spaced relation to the end of the rod in a planedisposed diametrically and axially of the rod and having an end boundedby a cutting edge in the tapered portion of the threads but overlappingsaid position and having an opposite end bounded by a cutting edgedisposed in the threads of uniform diameter and each end of the openingbeing positioned so as to be closed by the workpiece to capture thechips in the collecting bore when said end of the rod is inserted intothe stud opening sufficiently to bring the cutting edges into workpieceengagement.